This invention relates to a rotatable twist tube device for false twist texturing a continous filament thermoplastic yarn being passed through the twist tube, in which the twist tube constitutes the hollow shaft rotor of an electric motor.
Rotatable twist tube devices in which the twist tube constitutes the rotor of an electric motor are known in the art, for example in U.S. Pat. No. 3,656,290 of P. Kuussaari, which issued on Apr. 18, 1972, and in Canadian Pat. No. 947,587, which issued May 21, 1974 on an invention by E. L. Creelman et al. In such an existing rotatable twist tube device, friction bushings, each having rounded front friction surface, are positioned in the opposite ends of the hollow shaft rotor which comprises the twist tube. The hollow shaft rotor is mounted near each of its ends in a bearing means supported by the end housing of the motor. A continuous filament thermoplastic yarn passed through the hollow shaft rotor has a rolling twist imparted to it by the rounded surface of each of the two friction bushings as the hollow shaft rotor of the electric motor rotates at high speed.
A disadvantage of such an existing rotatable twist tube device becomes apparent when a break in the yarn occurs at either end of the hollow shaft rotor. The friction bushing at the end near the break may act as a winder and wrap the loose tail of yarn around the outside of the hollow shaft rotor behind the bushing. As turns of yarn build up, the yarn is jammed into the annular space between the end housing of the motor and the rotating hollow shaft rotor. Continued rotation of the hollow shaft rotor compacts the jammed turns of yarn into a tight wad of fiber which may cause one or more of the following to occur: (1) the motor to be stopped; (2) the stator winding of the motor to be overloaded causing overheating and frequently failure of the stator winding; and (3) in some instances, if the hollow shaft rotor continues to rotate, the wad of fiber works its way past the bearing seal and destroys the motor bearings. Once the wad of fiber has formed and jammed the motor, it is not possible for the operator on duty in the false twist texturing area to remove the wad of fiber and restring the texturing position. The motor has to be replaced by another unit and the jammed motor disassembled, cleaned and, if necessary, repaired.